Solar energy collection systems which utilize optical concentrators to focus incident sunlight on to small energy receivers offer many cost and performance advantages over flat-plate solar energy collectors. In heat collector applications, the energy receiver area loses heat to the environment by radiation, convection and conduction. Accordingly, receivers with smaller receiver areas would have smaller heat losses and operate more efficiently. In photovoltaic collector applications, such focussing collectors would also utilize much smaller quantities of expensive semiconductor materials such as silicon, due to the smaller receiver area. One particularly effective solar concentrator is the linear Fresnel lens system of U.S. Pat. No. 4,069,812. That collector system has been developed to provide efficient collection of heat, photovoltaic electricity, and a combination of both. However, due to the basic physics of linear Fresnel lens concentrators, the concentration ratio, which is defined as the lens aperture area divided by the illuminated receiver area, is practically limited to values between 25 and 50. It is highly desirable to provide higher concentration ratios of 100 to 200. Higher concentration ratios would allow the same radiant energy to be collected, for example, in a photovoltaic application, but would require significantly smaller solar photovoltaic cells thereby substantially reducing the cost of the system.